In modern control systems for internal combustion engines, the fuel quantity to be injected is determined on the basis of the air flow drawn into the engine. This quantity of fuel is pregiven by the driver via a control of the throttle flap which is achieved via a mechanical and/or electrical path. When the air flow is adjusted in dependence upon the command of the driver, the clocked operation of the engine is not considered and the throttle flap is held fixed in a predetermined position when the command of the driver remains constant. An engine equipped with this conventional control system, however, exhibits an unsatisfactory operating performance in various operating ranges and requires a high complexity with respect to the control and/or the components used.
This unsatisfactory operating performance relates, for example, to: (a) the trace of the torque in the full-load range supplied by the engine which shows dips for specific conditions in specific rpm ranges; (b) the efficiency of the preparation of the mixture in central injection systems which preparation is affected by the injection of the fuel onto the positioned throttle flap through which reduced air flow occurs especially in the lower load range with the mixture being unsatisfactory because of the wetting of the throttle flap; (c) the correction of the uniform fluctuations and other effects specific to a cylinder such as small fluctuations of the exhaust-gas composition and the like; these fluctuations must be corrected by intervening in the metering of fuel or in the ignition on the basis of comprehensive control programs; and, (d) the idle control where high resolution position sensors must be utilized because of the necessary precision for control via the main throttle flap.
U.S. Pat. No. 4,571,990 discloses that the ranges of increased backflow of air in the intake pipe can be detected with the aid of the reversal points of a signal supplied by an air-mass sensor.
U.S. Pat. No. 4,688,535 discloses measures for improving the smooth running of an engine wherein the uniform running of the cylinders is checked on the basis of a crankshaft signal and the cylinder or cylinders which depart from this uniform running can, if required, be detected and the uniform running can be reestablished by intervening in the metering of fuel.
U.S. Pat. No. 4,452,200 discloses an idle control equipped with a position control of the main throttle flap.